Separate packages addressed to Maryland Gov. Martin O'Malley and his secretary of transportation contained incendiary devices that flashed, smoked and produced an odor when they were opened Thursday, causing minor injuries to two employees and putting officials around the Washington region on alert.

Officials stressed that the packages were not mail bombs and that so far they have found no explosive material associated with either of them.

The package addressed to O'Malley (D), which came with colorful holiday stamps, was opened about 12:30 p.m. in the mailroom of the Jeffrey Building on Francis Street in downtown Annapolis. It singed the fingers of the worker who opened it but didn't cause any property damage.

About 15 minutes later, a similar package was opened with a flash, smoke and a sulfur smell at the Maryland Department of Transportation headquarters in Hanover. The worker who opened it was taken to a hospital as a precaution, but again, there was no property damage. Authorities said both parcels were about the size of a book.

Law enforcement officials said both packages contained notes, but they declined to say what the notes said. However, a note from the sender that accompanied the package to O'Malley contained a mocking reference to the phrase "report suspicious activity," saying it was "total [expletive]," according to a source familiar with its content.

O'Malley told reporters Thursday night that the phrase might be a reference to the sender's displeasure with overhead highway signs.

Maryland State Fire Marshal William E. Barnard said he was unaware of any threats to state officials.

The devices caused about as much harm as they were capable of, officials said. "It would be wrong to characterize it as a bomb," Barnard said. "There was no explosion."

Maryland and federal officials said the packages did not explode, and they characterized them as incendiary devices. State officials are leading the investigation, with help from federal agencies.

But for a while Thursday afternoon, there was a frenzy and fear that there would be more-serious undiscovered devices. Officials evacuated the affected buildings, blocked nearby roads and quarantined all state mailrooms.

"We didn't know what we were dealing with at the time," O'Malley said.

O'Malley, who said he had spoken to the worker who opened the package addressed to him, called the incident "a reflection of the times we're living in."

"Fortunately, no one was hurt, and these were not devices of the sort that could hurt, but it underscores how vigilant we need to be," O'Malley said in a brief interview as he arrived in Cambridge, Md., for a dinner with county leaders from across the state.

After the incidents, District officials stopped government mail delivery, and Virginia authorities said they were closely monitoring the situation. The University of Maryland put out an alert that no mail was to be opened.

Maryland's U.S. senators, Barbara A. Mikulski (D) and Benjamin L. Cardin (D), sent a letter to FBI Director Robert S. Mueller III commending the quick federal response and saying they were "troubled by this apparent attempt to harm the hardworking men and women who serve the people of Maryland."

"Should the incidents prove to be acts of terrorism," they wrote, "we ask that you commit the appropriate resources . . . so that the perpetrators are caught and brought swiftly to justice."

O'Malley was in a meeting at the State House when he was informed about the devices.

Transportation Secretary Beverley K. Swaim-Staley was on the fourth floor of the department's headquarters when the package addressed to her was opened on that floor, officials said.

The state fire marshal's office, Maryland State Police, the FBI, the U.S. Postal Service and the Bureau of Alcohol, Tobacco, Firearms and Explosives have joined the investigation, authorities said.

As the evening wore on, packages at the Maryland Department of Health and Mental Hygiene in Baltimore and the federal courthouse in Baltimore were deemed suspicious. But the situations were cleared without incident, authorities said.

"We have collected a significant amount of physical evidence, and believe me, we are going to get to the bottom of this," Barnard said.

State police spokesman Greg Shipley said the package addressed to O'Malley at 100 State Circle included a complete Zip-plus-four code. Five colorful 44-cent holiday stamps were affixed to it, bearing images of a gingerbread man, a snowman, a nutcracker soldier and reindeer.

Officials said the parcel sent to the Transportation Department, near Baltimore-Washington International Marshall Airport, was about a foot long, between four and eight inches wide, and an inch thick.

A state worker said that when that package was opened, the fire alarm went off, and people at first assumed it was a drill. About 250 workers were evacuated, but the building was reopened later in the evening, authorities said.

Both packages were sent through the U.S. mail, said Frank Schissler, a postal inspector. He said that when opened, they produced flame and smoke.

Schissler said such incidents are extremely rare. Since 2005, he said, U.S. postal workers have delivered a trillion pieces of mail, and 13 mail bombs have been discovered. One person was injured in those incidents, he said.

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